NEESR: Tsunami Run-up and Withdrawal Dynamics on a Sloping Beach with Discontinuous Macro-Roughness

What

Tsunamis are a leading natural threat to coastal communities, and events such as the 2011 Japan, 2010 Chile, and 2004 Indian Ocean tsunamis caused widespread, crippling damages to coastal infrastructure. Yet, these events also revealed the role of mangroves and other vegetation as sustainable mitigation against tsunami hazard. The overarching goal of this research is to develop a quantitative understanding of tsunami inundation in regions with coastal forests. This project combines detailed fluid dynamics modeling with physical experiments to study tsunami inundation in the presence of discontinuous coastal forest. Laboratory experiments will be used to study inundation in discontinuous forest, represented by circular patches of cylinder arrays. Measurements will be used to quantify mean flow and turbulence statistics, the spatial flow field between two forest patches, runup speed, and large-scale flow structures during withdrawal. Numerical analysis will be integrated with the experimental campaign to expand the parameter set for analysis and to assess the impact of temporal changes in forest characteristics.
NSF award abstract

When

Spring 2013

Equipment

Tsunami Wave Basin

PI

Co-PI(s)

James Kaihatu, Texas A&M

Alexandru Sheremet (U Florida),
Robert Weiss (Virginia Tech)

Title

NEESR: Interaction of Tsunamis with Short Waves and Bottom Sediment - Numerical and Physical Modeling

What

The interaction between short ocean waves and long transient tsunamis is studied in conjunction with sediment transport process. This is in keeping with the theme of the study of tsunami-generated processes in concert with natural oceanographic processes, and will be done from two viewpoints: that of the tsunami's effect on the transported and reworked sediment bed; and that of the effect of the sediment load on the transporting power of the tsunami. Numerical modeling will form the backbone of this work, with physical modeling providing data for process study, parameterization and validation. A sophisticated model based on smoothed particle hydrodynamics will be tightly integrated into the experimental plan. The first set of experiments at OSU will focus on evaluating the transport power of the tsunami in order to develop the pickup function and other parameterizations for the transport model. The second set of experiments will investigate full bed evolution. In all experiments, forcing will consist of tsunamis and combined tsunami-swell conditions. Measurements will be used to evaluate the dissipation of the tsunami in several different ways.
NSF award abstract

Based on the observations during the 2004 Indian Ocean tsunamis, it is evident that the leading tsunami waves could have various forms: undulating bores and long waves with a leading depression. It is certain that theses leading waves are not solitary waves. A new paradigm needs to be established for experimental tsunami research. As tsunamis inundated and flooded the land, they often left behind widespread sediment deposits. If the properties of tsunami deposits can be correlated with the flow depth, velocity, and wave characteristics of tsunamis, the dated deposits will allow estimates of times and recurrence intervals of past tsunamis. Since the sediment transport processes are primarily driven by the flow turbulence and bed shear stresses, it is essential to have an in-depth understanding on the evolution of near bed flows driven by the leading waves of tsunamis, in particular the bed shear stress.

The research activities will cover two years of testing and include the development and implementation of new tsunami algorithms for the new wave maker at the large wave flume as well as the design and fabrication of a instrument package for measuring bottom shear stress.
NSF award abstract

When

Jan 2013

Equipment

Large Wave Flume

PI

Co-PI(s)

Ron Riggs, Univ of Hawaii

Dan Cox (OSU), Clay Naito (Lehigh), Marcel Kobayashi (UH)

Title

NEESR-CR: Impact Forces from Tsunami-Driven Debris

What

The objective of this research project is to improve our understanding of, and predictive capabilities for, tsunami-driven debris impact forces on structures. Of special interest are shipping containers, which are virtually everywhere and which will float even when fully loaded. The forces from such debris hitting structures, for example evacuation shelters and critical port facilites such as fuel storage tanks, are currently not known. We will carry out experiments at NEES@OSU and NEES@Lehigh to improve our understanding of low speed impact of heavy debris and to develop and validate two numerical models: a simplified model that can be used for design, and a more complex fluid-structure interaction model based on computational fluid dynamics. This simulation-based model will allow us to explore complex parameters not included in the simple model and to consider scenarios not covered by experiments.
NSF award abstract

Within the last decade, broad sections of the Oregon-Washington
continental shelf located in the northern California Current System
have been affected by severe hypoxia during the summer upwelling
season. Mass balances of dissolved oxygen on the shelf indicate oxygen
uptake of sediments is greater than estimated from benthic flux
measurements using traditional benthic chambers and microprofiles.
The most probable explanation for this inbalance is uncharacterized
temporal and spatial variability in the major physical and biological
processes contributing to on-shelf oxygen utilization. A scientist
from Oregon State University (OSU) plans to determine the magnitude
and variability of benthic oxygen fluxes on the inner and middle
Oregon shelf and the contribution of wave-induced motions to these
fluxes using the eddy correlation (EC) technique. Initially, EC
measurements in the presence of energetic waves will be studied in
the Large Wave Flume at Oregon State University.
NSF award abstract

The overarching theme of this effort is to formulate the complex processes
affecting our coastal structures that are driven or affected by
turbulent coherent structures (TCS). The role of wall bounded TCS in
multiple forcing environments will be examined. Near the seabed,
sediment pickup and transport can be significantly enhanced by TCS,
leading to extreme scour and infrastructure failure. In the horizontal
plane, TCS can appear as giant whirlpools and are commonly associated
with extreme damage in ports and harbors. Extensive experiments will
be performed at the Oregon State University, using the Large Wave
Flume to study the fine detail of TCS significance on nearbed
processes, such as mobilization and transport of sediment, as well
as the Tsunami Wave Basin to characterize the complete hydrodynamic
structure of a large, horizontal TCS generated by a port. The
observations will be complimented with a wide-reaching numerical
effort.
NSF award abstract

This project's long-term goal is to transform assessment and mitigation of the
landslide tsunami hazard through hybrid modeling of landslide tsunami evolution in
real world scenarios, where the generation, propagation, and runup stages overlap.
Rare field measurements are mostly limited to landslide scarp, deposit, tsunami runup,
and eyewitness accounts, while critically important data related to the landslide
motion and tsunami evolution is lacking. The goal of the research is to compensate
for missing data by combined physical and numerical modeling of fully three-dimensional
landslide tsunami scenarios.
NSF award abstract

Based on the observations during the 2004 Indian Ocean tsunamis,
it is evident that the leading tsunami waves could have various
forms: undulating bores and long waves with a leading depression.
It is certain that theses leading waves are not solitary waves.
A new paradigm needs to be established for experimental tsunami
research. As tsunamis inundated and flooded the land, they often
left behind widespread sediment deposits. If the properties of
tsunami deposits can be correlated with the flow depth,
velocity, and wave characteristics of tsunamis, the dated
deposits will allow estimates of times and recurrence intervals
of past tsunamis. Since the sediment transport processes are
primarily driven by the flow turbulence and bed shear stresses,
it is essential to have an in-depth understanding on the
evolution of near bed flows driven by the leading waves of
tsunamis, in particular the bed shear stress.

The research activities will cover two years of testing and
include the development and implementation of new tsunami
algorithms for the new wave maker at the large wave flume as
well as the design and fabrication of a instrument package
for measuring bottom shear stress.
NSF award abstract

When

Spring/Summer, 2011

Equipment

Large Wave Flume

PI

Co-PI(s)

Daniel Cox, Oregon State

Rakesh Gupta, Oregon State
John van de Lindt, Colorado State
Francisco Aguiniga TAMU-Kingsville

The goal of this project is to model building damage by studying
water flow and debris hazard of collapsed buildings in the flooded
areas. This will help us understand the expected damage to cities
and town and to design buildings to withstand these forces.

As a first step of this new approach, we will focus on residential
(light-frame wood) buildings which make up 90% of the building
stock in the US and are where people spend approximately half of
the hours in their day, Because of the sheer number of residential
buildings in these coastal communities, understanding tsunami
impact on these structures and the expected damage level is
necessary to reduce damage and loss of life.

Phase I of this project took place in the Large Wave Flume in FY2009. Phase II will
take place in FY2010 in the Tsunami Wave Basin. Their work will focus on tsunami
structure tests at the 1:4 scale, and utilize the three-dimensional ability of the
TWB wavemaker to better understand the effects of shadowing by multiple objects
NSF award abstract

This payload project will investigate how tsunami waves are amplified by interaction
with ocean swell and wind waves. Understanding how different ocean conditions can
change the destructive power of tsunami waves is crucial in planning evacuation
strategies. The TWB wavemaker will be directed to produce these novel conditions
and the wave climate and water velocities at various locations will be measured.

The project will share instrumentation and space with the Cox NEESR project.
NSF award abstract

This payload project will utilize the north portion of the TWB to investigate
macro-roughness elements and their affect on tsunami runup. Specifically, the
project will be investigating the impact of coastal vegetation on tsunami wave
dissipation by placing large scale macro-roughness elements in the basin.

The project will utilize instrumentation setup by the NEESR project to measure the
wave climate, as well as velocity measurements at specific locations.
NSF award abstract

When

Summer 2010

Equipment

Tsunami Wave Basin

PI

Philip Liu, Cornell University

Title

EAGER: Developing and Testing Algorithms for Generating
Leading Tsunami Waves

What

During the last forty years, solitary waves have been used as
surrogate leading tsunami waves in laboratory studies. The data taken from
the 2004 Indian Ocean tsunamis, however, show that the length and time
scales for the solitary wave are too small in comparison with those of real
tsunamis. This discovery poses a fundamental challenge for the tsunami
research community, who currently interpret the existing results based on
solitary wave theory. More importantly, this points to the need to
investigate the feasibility of generating adequate long waves in a
laboratory facility for laboratory research.

This research will use the newly installed wave makers with long strokes at
the NEES tsunami facility at Oregon State University to test the hypothesis
that the leading tsunami wave does not have sufficient time and distance to
evolve into a solitary form, therefore challenging the currently used
modeling approach for wave runup and other physical quantities based on the
solitary wave.
NSF award abstract

When

Winter 2010

Equipment

Tsunami Wave Basin

PI

Co-PI(s)

Daniel Cox, Oregon State

Rakesh Gupta, Oregon State
John van de Lindt, Colorado State
Francisco Aguiniga TAMU-Kingsville

The goal of this project is to model building damage by studying
water flow and debris hazard of collapsed buildings in the flooded
areas. This will help us understand the expected damage to cities
and town and to design buildings to withstand these forces.

As a first step of this new approach, we will focus on residential
(light-frame wood) buildings which make up 90% of the building
stock in the US and are where people spend approximately half of
the hours in their day, Because of the sheer number of residential
buildings in these coastal communities, understanding tsunami
impact on these structures and the expected damage level is
necessary to reduce damage and loss of life.

The goals of this NEESR-II project are to (1) develop a methodology
to assess the risk of residential structures to tsunami inundation
and wave forces through a systematic experimental study coupled
with a numerical probability of failure analysis; (2) enable the
development of innovative retrofit products by developing a
structural testing protocol that is representative of hydraulic
impact/forces during a tsunami; and (3) refine the current
hydraulic force equation in ASCE 7 based on a series of wave basin
tests to account for building density and other variables. This
transformative project builds on the knowledge base of tsunami
inundation at regional scales and the tsunami-structure
understanding at the building scale from other NEESR projects.
This project also integrates new large-scale physical modeling
and numerical modeling efforts to mitigate both structural risk
to building damage and loss of life in a community-wide tsunami
inundation event.
NSF award abstract

The objectives of the proposed research program are to 1) improve understanding of
nearshore, three-dimensional tsunami evolution through an extensive set of physical
experiments using NEES facilities; 2) create an extensible framework to provide a systemat
ic
structure for validating computational models with experimental and field data; 3) refine
modeling capabilities and couple the various components together to create a multi-scale
simulation tool; and 4) develop a sustainable education and outreach program that educate
s
the general public about tsunamis and appropriate responses to them. Nearshore evolution
of
tsunami waves, such as 3D breaking through focusing and bathymetry, and overland flow
across irregular and rough topographies, will be investigated. Concurrent to the experime
ntal
effort, a comprehensive tsunami simulator, TSUNAMOS (Tsunami Open Source Community Model)
,
will be developed.

Phase III, the third and final phase of this project, will begin in May
2009. Based on the results of data analyzed from phase II, researchers will
construct a bathymetry with a significant cross-shore feature, such as a
channel, which will generate strong 3D changes in the flow patterns during
runup and rundown. This feature will be designed to mimic a realistic
shallow water bathymetry irregularities, and will provide insight into the
magnitude of flow variations due to such local features. Free surface maps
will be created, and turbulence information will be extracted from numerous
velocity measurements. In addition, overhead video and dye studies will be
used to visualize flow patterns.
NSF award abstract

Phase III of the NEESR-SG project to develop Performance Based Tsunami Engineering
(PBTE) will utilize the new tsunami wavemaker in the Large Wave Flume (LWF) to
repeat experiments already performed in the Tsunami Wave Basin (TWB) during phase
II testing. Based on the results of extensive test runs in the TWB from June to
December 2007, selected experiments will be repeated at 2.5 times the scale in the
LWF. This will allow for evaluation of scaling techniques so that both TWB and
LWF test results can be extrapolated to full scale conditions. Tsunami bore
formation and energy dissipation studies will focus on the effect of various bed
profiles applied to the beach slope and flat reef regions. Structural loading
tests will focus on uplift on floor systems and lateral loads on column and wall
elements when struck by a tsunami bore.
NSF award abstract